Method and electric circuit arrangement for neutralizing capacity coupling



Mar. 27, 1923.

L. A. HAZELTINE METHOD AND ELECTRIC lCIRCUIT ARRANGEMENT FORNEUTRALIZING CAPACITY COUPLING Filed Aug. 7, 1919 3 sheets-.sheet l FIG.c?.

"Mar: 27, 1923. 1,450.08@

A. HAZELTINE METHOD lAND ELECTRIC CIRCUIT ARRANGEMENT FOR NEUTRALIZINGCAPACITY COULING- Filed Aug. '7-, 1919 3 sheeVt's-sheet 2 Mar. 27;19.23." 1,450,08)l

. L.. A. HAZELTINE METHOD AND ELECTRIC CIRCUIT ARRANCEMENT FCRNEUTRALIZING CAPACITY COUPLING Filed Aug. '7, 1919 5 sheets-sheet 3`Poema Mu. 21, i923,

UNITED iSTATES PATENT OFFICE.

LOUIS A. HAZILTINE, 0F HOBOIEN, NEW JERSEY.

muon am) gnnc'rsrc CInCUI'I` ARBAHGHENT IOR NEUTELLIZING COUPLIIG.

CAPACITY Anneau@ ala ang-n 7, ma. semi n. 316,007.

. of capacit Acoupling between two electric circuits, w ich capacity'coupling results in the transmitting `from-one circuit to the other."

15,' ItV has long been known from practical experience that thepresence'of capacity,

coupling between the primary and secondary circuitsl of a radio receiverresults linthe transmitting of undesired signal oscillations,

l) 4particularly those of short wave length, from the primary to thesecondary circuit. This reduces the selectivity of the receiver andfrequently prevents the reception of the .desired signal, which isdrowned'out by a more la powerful signal of a different wave-length.Twofmethods have Ybeen .used to reducethe capacity coupling; rst,thephysical sc pal ration ofl the two circuits by as great a istance asisfeasible; and second, the partial enclosing of the 'circuits in metalscreens.

. Neither method is entirely effective, for thereuire an impracticablywideA f t first would separation-o e circuits; while in the sec-v ondthe-metal screens could not completely l'enclose'. the circuits as Atheywould then prevent the desired magnetic coupling. s "Again, it is wellknown that capacity cou-V pling between the grid and plate circuits ofau audion nia result in the production of oscillations. uch oscillationsare4 Yfrequently very undesirable, particularly in audion am lilers, asthey may completely Y the signal which it is desired to .am-

- As a third example of the undesirable effects of capacity vcouplingithas been found difficult to arrange a Wheatstone brid for high-frequencymeasurements, due to t e capacity coupling between the supply circuitand' the detector circuit, which may result in a false balance and sovitiate the results of the measurements.

cou ling between two circuits such as are deof undesirable disturbancesc1rcu1t diagram 'asjused in the moet a vanced type o'f-re"- Thisinvention is directedto the elimina- Vtion of the undesirable effects ofcapacity scri d 1n the foregoing examples. This is accomplished brieflyas follows: An auxiliary circuit is provided which iselectromagnetically coupled to one of the two original circuits which wewill call the' first circuit, and capacitively coupled to the other, orsecond circuit. If a disturbing volta then exists in the second Circuit,it will Acause currents'fto flow both inthe rst circuit a nd intheauXIaR circuit, due to the capacity coupllngs. e electro-magneticcouphng between the auxiliary circuit and the first circuit is thenarranged so that the magnetic effects of these two currents will.

neutralize one another and so will result in 'Il no volta e across" thefirst circuit. Conversely, if a disturbing voltage exists in the firstcircuit, it will` result in no voltage across the second circuit, by theWell known reciprocal properties of electric circuits.

,The arrangement of the auxiliary circuit will depend on the forms ofthe original circuits. In some cases it is necessary to add coils orcapacities fo the original circuits to provide the required couplinwhile in other cases the couplings may obtained Vfrom coils present forother purposes or from inherent capacities. ,ff

The' principle and certain applications of this invention areillustrated 1n the accompanying drawings in which Figure 1 is a showingtwo capacitively coupled circuit elements which are not d1-v rectlyconnected, andthe arrangement fcr neutralizing this capacity coupling;Figure 2 -is a corresponding *diagramv or t e case of two circuit'eements directly connected; Figure 3 is a vwiring showing thea'rrangement for neutralizing ca acity couplingbgtween the primary ansecondary circuits `of a radio receiver; Fi re 4 is a cross-section ofthe coupling coils and the auxiliary coil in a radio receiver; Figure 5shows a preferred arran ment of these coils l ceiver built for theUnited States Na Figure 6l is a circuit diagram showing t arrangementfor neutralizing capacity coupling between the grid and plate circuitsof n? VAand C, remaining the coupling capacities.

an audion; Figure 7 is a circuit diagram, showing the arrangement forneutralizing capacity coupling tied form of secondary winding whichv maybe utilized as an alternative to the arrangement shown in Fig. 4. f

Referring to Fi re 1, reference characters A and B indicate the circuitelements having undesired capacity coupling thru the capacities C, andC3 and thru the imedances Z and Z". Reference character 1 indicates acoil which may be part of circuit elenient A or may be additionalthereto; L2 represents the auxiliary coil closely coupledelectro-magnetically to L1 and thence to circuit element A, and at thesame time capac' itively coupled to circuit element B through capacitiesC2 and C1. The sense of electromagnetic cou lin between L and L2 is suchthat termina s' o lunlike po arity are connected together. To understandthe principles of this arran ement, first suppose that the two coils area ike and are very closely coupled, that (CF1-TG2) and that (C3:C,).Also suppose, just for the moment, that A is removed; then by symmetry asource of voltage in B will cause equal currents totlow through L1 andL11'Which currents will neutralize one another magnetically; so novoltage will be induced in eitherl coil. Now if A is replaced, it willbe connected betweenA two points having no difference in potential andso willnot alter the electrical conditions, assuming the resistances ofthe coils negligible in comparison with their separate re- ,actancesment B will not result in a voltage across circuit element A so theeffects of capacity cou ling will have been neutralized. Y A oregenerally in Figure 1, suppose the to be unlike, though still L2 -to L,is N1/N1, then we must have .0, Cs N,

C, Ct N1' in which case' the currents of C1, C1 and L1 will be Nz/N1times the currents of. 0 CM and L1, respectivel and the magneto-motiveforce of L2 will still neutralize that of L, giving no induced voltagein either coil.

lt should 'be noted that the above conditions for neutralization imposeno limita- '1 tions on the internal conditions in 'circuit elements Aand and Z.

If the impedance Z','

B nor on the values l.of Z

of Figui@ 1 is relaced bv a direct connection, the capacities;-

1 and C4 are directly in parallel with vA and L2, respectively, and sono longer act as couplin capacities. This circuit in effect becomes't atofFigure 2, where the` same reference characters refer to like parts, Cl

i to the detector circuit of a Wheatstone bridge; and Fig. 8 is a modi-Vinsulated therefrom by insulator 1,5.

Thus the voltage in circuit ele-Y 'ducingthe capacities C, and C, by

Thr condition. for neutralization, as before, is simply v 'and 3 bymetal partition 4. This metal lining is grounded as at 5. The antenna 6is connected thru the primary coil -7 of the coupler 8 and variablecondenser 9 to the metal'lining connected to' earth 5. The anl tennalead passes -thru the metal walled cabi.- net but is insulatedtherefromby insulator l0. The secondarycoil L, of the cou ler havingterminals 12 and `13 is connected at one end thru lead 13a withdetecting appa- A ratus in compartment 3 and at the other end tothemetal lining 1 by means of lead 12. The lead 13 passes thru partition 4and is The detecting apparatus in compartment 3 may be composed of asuitable circuit'inducta'nce 16, variable condenser 17 grounded at 18and `leads 19 taken to the usual detector, preferably an audion. Themoving elements of the condensers 9 and 17 are those connected toground; so that no external capacterminal 12 and free ended at Aterminal21.

This auxili coil; is Wound over secondary coil L1 but in oppositedirection thereto, from terminal 12 as a starting point.

By the arrangementof the apparatus as above described in compartment 2and 3 it'will be seen that the only possibility of capacity couplingbetween 'the' primary and secondary circuits lies in the inherentcapacities C, and C11, between primary coil 7 and the seconda T coil.L1. This capacity coupling is neutra ized by the auxiliary fcol L2 andthe inherent capacities C1, and C4 present by reason of the addition ofcoil L1. In actual construction the turns of coil L2 are wound over theturns of secondary coil L giving close-magnetic coupling and retheirscreening action. The circuit of Figure 3 lis thus a s ecial applicationof the general tically, the primary coil 7 of Figure 3 correlltl theratio of turiis"N,/l\'1 of the coils respectively. The secondary coilhas -its iary coil L, is closely `coup 1,450,0eo B i sponding to thelcircuit element B of Figure To neutralize'. i apacity coupling. the i1, the portion of the secondary'circuit in auxiliary coil 12,1islclosely coupled e compartment 3 .corresponding tothe circuitmagneticallytofthej grid coil L1 'and is conelement the antenna-groundcircuit 6 to' nected abetween'wthlament and'tlie neuv 5 corresponding tothe impedance Z and the tralizing capacity; whose' other. terminal 701arbitrarily variable condenser 9 correspond` is connected to "t e plate.This circuit is ai ing to the impedance, Z. Neutralization of s iecialapplication" of thegeneral circuit of the capacity coupling willtherefore be' at- Iigure2; and-neutralization of thecapacity tained', asin Figure I1, when the capacity coupling duc to C, will be attained, asin ratios (l1/C2 and C3/C, are madee ual to Figure 2, when theratiooff'ca 'cities l/C, 75

(la, and. is v made equal to the ratio. opturns N,/N1 L1, respectively.The turns of L, are ad-A ofthe coils L,and L1, respectivel justed bytrial and will be less than those Figure 7 illustrates the applicationof this on Ll as the capacities'C, and C4 exceed invention to theneutralization ofthe ca ac- -C1 and C, respectively. The symmetry of'.-it-ycouplin tothe detector circuit of ahi'gh0 4 the arrangement isrelied on to maintain ap frequency heatstone bridge. The detectorproxiinate equality between (J1/C2 and is connected across the secondarycoil Ll of C,/C even when .the coils L, and L2 are a transformer whoserimary coil L ismoved relativeto coil 7 to secure variations connectedbetween the etector pointsof the in electro-magnetic coupling betweenthe bridge proper. The detectorfcircuitliscapau primaryandsecondarycircuits: citively coupled to the bridge proper'through igure 4is a crosssectional view showing the inherent capacities andil C, andthe -arran ment of the. primary, secondary through the .bridge arms andground; To and auxi iary couplel coils 7, LL and L neutralize 'thiscapacity coupling theauxil ed e ec'tro-mag- .0 high-potential end 13connected through the net ically tol L1 and capacitively coupled tosecondary inductance 16 to the detecting ap. the bridge proper thru theneutralizing. ca-

' paratus as describedand the auxiliary coil pacit-ies' C, and 0,. -Thiscircuit is a special starts at the terminal 12 of the secondaryapplication of the-general circuit of F ig-4 coil and doubles back overthe secondary ure 1 andneutralizationof -the capacity. coil in theopposite directionwith the end couplin will be: attained as in F igul'e1,

21 left free.' The auxiliary coil is suitablywhen t e capaci supportedover secondary coil Lnb insuare made equal 'ratioof'turns vN,/N1 latingdrum 20. In case the lead 1' from ofV the coils El,.vi'epectivelyl It isthe upper terminal 13 of L1 has appreciable dcsirableto.pla'c'e'tlicaux'ilia coil L, be- 100 capacity this may be neutralizedby means tween" L i of the arrangement shown in Fig. 8 wherein C1 andjf'by l itsefscreing actiong5 in. a dumm lead 21* is shown connected to theYFigure '4; Y' terminalY the lcad 13. The alternative arrangement Iclaim Aand Vdesire vto secure. by- Letters '105 oil.v Fig.. 7 includes"an 'additional auxiliary Patent of the, United States is:

coil L2 Wound inside"l the SGCOndlllj' "QOH L1 '1. In a system of twoelectric circuits and capable of bein rotated by means of inversev ratioof the'- capacities with which pling.

' fimpedence Z. Reference c the purpose of which is to proyide morecoupled through a junction point and complete screenin Each of thec'oils L1, through a capacity, means forneutralizin L, and L', is preerably grounded as shown the capacity coupling comprising a coil u at12. connected between said junction pointv and Figure 5 is a sectionalview of the preone terminal of said coupling capacity, and ferredarrifngement of the coupling coils an auxiliary coil and aneutralizingcapacity wherein the primary coil 7 is rigidl mountunequalto'the coupling capacityconnected ed on panel 22 by supports 23 an 24,Secbetween said junction pointl and the other 115 ondary coil L1 andauxiliary coil L, insu-v terminal of the coupling capacity, said coilslated therefrom by-suitable insulation 20 being lclosely coupledelect-romagnetically are .wound on frame 25 mounted on shaft 26 andhaving av ratio of turns equal to the knob 27 to obtain' di erentdegrees of cou-A they are respectively associated.

2. In a system of two electric circuits-in Figure 6 illustrates theapplication of this which an element of one circuit has one terinventionto the-'neutralization of the capaminal connected to the second circuitcityV coupling between the gridA and plate through coupling Vimpedancesand has its 21 of L, and disposed alongside'f 4Having thus described-myinvention, whatV circuits of an audion, the grid circuit conother-terminal connected to the'second cirmi taining. a coil L, and the platecircuit an cuit through a group of coupling capacities, 'ancter C,inmeans. for neutralizing sai couplingY c omdicates the inherentcoupling capacity, partj prising'a coil connected between said ter- V ofwhich iswithin the audion and part be i minals and anauxiliarv coilclosely coupled tween theleadsto the grid and the plate.electromagneticallytothe first coil and conl vnecte'd between the firstmentioned terminal and the common terminal of. a group. of neutralizingcapacities, each of which extends to said second circuit, is associatedwith one couplingcapacityfand has a ratio to its associated Vcouplingcapacity equal tothe inverse ratio of turns of the 'auxiliary coil tothe first coil.

3. In a. system-of two electric circuits in which an element of onecircuit has one ter mina] connected to the second circuit throughcoupling impedances and has. its other terminal connected to the secondcircuit through a pair ofv coupling ca acities, means for neutralizingsaid coup ing comprising a coil connected between said terminals and anauxiliary coil closely coupled electromagnetically to the first coil andconnected between .the first mentioned. terminal` and the commonterminal of a air of neutralizing capacities, each oi w ich extends tosaid second circuit, isassociated with one v coupling capacity, andv'hasa ratio to its which an element of one circuit' has one associatedcoupling ea acityequal to the in verse ratio of turns oi) the auxiliarycoil to the first coil.

4. In a system of two electric circuits-in terminal connected-to" thesecond circuit through arbitrarily variablev coupling impedances and hasits'p'other terminal connected to the -second 'circuit throu h- .a groupof coupling capacities, means or .neutralizing said'coupling comprisinga coil connected between said terminals and `an auxiliary coil closelycoupled electromagnetically tothe first coil and connected' between thef first mentioned terminal' and the 'common ter-- minal of a groupv ofneutralizing capacities,

each of which extends to said second circuit, is vassociated with onecoupling capacity, and has a ratio to its associate coupling capacityequal ,to the inverse ratio of turns of theY I gether, said auxiliarycoil beinginterposed f in the electro-static field created between vsaidcoil and said circuit.

6. ,In a Wave signalingresponsive device comprising a primary circuitand a secondary circuitl the combination of a conducting screenelectro-statically isolating the secondary from the primary -circuitsexcept-for a pair of coupling coils and an auxiliary coilelectro-magnetically coupled and connected to one of said coupling coilswith terminals of Aunlike polarity connected together, said auxiliarycoil havingfcapacity coupling to the other of said cou ling coils.

7. In a wave sign ingresponsive device comprising a primary circuit anda secondary circuit, the combination of a conducting screenelectro-statically isolating the secondary from the primary circuits exceptpfor a pair of coupling coils, and an auxiliary 4coilelectro-magnetically coupled and connected to one oi said coupling coilswith terminals of unlike polarity connected together, said auxiliarycoil being interposed in the electro-static field created between saidcoupling coils.

Louis A. HAZELTINE.

